Arabidopsis ETHYLENE INSENSITIVE 3 directly regulates the expression of PG1β-like family genes in response to aluminum stress

Ethylene is the key phytohormone to enhance arsenic resistance in Arabidopsis thaliana

The toxic metalloid arsenic is prevalent in the environment and poses a threat to nearly all organisms. However, the mechanism by which phytohormones modulate arsenic resistance is not well-understood. Therefore, we analyzed multiple phytohormones based on the results of transcriptome sequencing, content changes, and related mutant growth under arsenic stress. We found that ethylene was the key phytohormone in Arabidopsis thaliana response to arsenic. Further investigation showed the ethylene-overproducing mutant eto1-1 generated less malondialdehyde (MDA), H2O2, and O2•- under arsenic stress compared to wild-type, while the ethylene-insensitive mutant ein2-5 displayed opposite patterns. Compared to wild-type, eto1-1 accumulated a smaller amount of arsenic and a larger amount of non-protein thiols. Additionally, the immediate ethylene precursor, 1-aminocyclopropane-1-carboxylic acid (ACC), enhanced resistance to arsenic in wide-type, but not in mutants with impaired detoxification capability (i.e., cad1-3, pad2-1, abcc1abcc2), which confirmed that ethylene regulated arsenic detoxification by enhancing arsenic chelation. ACC also upregulated the expression of gene(s) involved in arsenic detoxification, among which ABCC2 was directly transcriptionally activated by the ethylene master transcription factor ethylene-insensitive 3 (EIN3). Overall, our study shows that ethylene is the key phytohormone to enhance arsenic resistance by reducing arsenic accumulation and promoting arsenic detoxification at both physiological and molecular levels.

Exploring Aluminum Tolerance Mechanisms in Plants with Reference to Rice and Arabidopsis: A Comprehensive Review of Genetic, Metabolic, and Physiological Adaptations in Acidic Soils

Aluminum (Al) makes up a third of the Earth's crust and is a widespread toxic contaminant, particularly in acidic soils. It impacts crops at multiple levels, from cellular to whole plant systems. This review delves into Al's reactivity, including its cellular transport, involvement in oxidative redox reactions, and development of specific metabolites, as well as the influence of genes on the production of membrane channels and transporters, alongside its role in triggering senescence. It discusses the involvement of channel proteins in calcium influx, vacuolar proton pumping, the suppression of mitochondrial respiration, and the initiation of programmed cell death. At the cellular nucleus level, the effects of Al on gene regulation through alterations in nucleic acid modifications, such as methylation and histone acetylation, are examined. In addition, this review outlines the pathways of Al-induced metabolic disruption, specifically citric acid metabolism, the regulation of proton excretion, the induction of specific transcription factors, the modulation of Al-responsive proteins, changes in citrate and nucleotide glucose transporters, and overall metal detoxification pathways in tolerant genotypes. It also considers the expression of phenolic oxidases in response to oxidative stress, their regulatory feedback on mitochondrial cytochrome proteins, and their consequences on root development. Ultimately, this review focuses on the selective metabolic pathways that facilitate Al exclusion and tolerance, emphasizing compartmentalization, antioxidative defense mechanisms, and the control of programmed cell death to manage metal toxicity.

Genome-wide identification of GA2ox genes family and analysis of PbrGA2ox1-mediated enhanced chlorophyll accumulation by promoting chloroplast development in pear

BACKGROUND

Chlorophyll (Chl) is an agronomic trait associated with photosynthesis and yield. Gibberellin 2-oxidases (GA2oxs) have previously been shown to be involved in Chl accumulation. However, whether and how the PbrGA2ox proteins (PbrGA2oxs) mediate Chl accumulation in pear (Pyrus spp.) is scarce.

RESULTS

Here, we aimed to elucidate the role of the pear GA2ox gene family in Chl accumulation and the related underlying mechanisms. We isolated 13 PbrGA2ox genes (PbrGA2oxs) from the pear database and identified PbrGA2ox1 as a potential regulator of Chl accumulation. We found that transiently overexpressing PbrGA2ox1 in chlorotic pear leaves led to Chl accumulation, and PbrGA2ox1 silencing in normal pear leaves led to Chl degradation, as evident by the regreening and chlorosis phenomenon, respectively. Meanwhile, PbrGA2ox1-overexpressing (OE) tobacco plants discernably exhibited Chl built-up, as evidenced by significantly higher Pn and Fv/Fm. In addition, RNA sequencing (RNA-seq), physiological and biochemical investigations revealed an increase in abscisic acid (ABA), methyl jasmonate (MeJA), and salicylic acid (SA) concentrations and signaling pathways; a marked elevation in reducing and soluble sugar contents; and a marginal decline in the starch and sucrose levels in OE plants. Interestingly, PbrGA2ox1 overexpression did not prominently affect Chl synthesis. However, it indeed facilitated chloroplast development by increasing chloroplast number per cell and compacting the thylakoid granum stacks. These findings might jointly contribute to Chl accumulation in OE plants.

CONCLUSION

Overall, our results suggested that GA2oxs accelerate Chl accumulation by stimulating chloroplast development and proved the potential of PbrGA2ox1 as a candidate gene for genetically breeding biofortified pear plants with a higher yield.

Melatonin alleviates aluminum toxicity by regulating aluminum-responsive and nonresponsive pathways in hickory

Aluminum (Al) toxicity is a significant constraint on agricultural productivity worldwide. Melatonin (MT) has been shown to alleviate Al toxicity in plants; however, the underlying mechanisms remain largely unknown. Here, we employed a combination of physiological and molecular biology techniques to examine the role of MT in mitigating Al toxicity of hickory. We found that MT decreased the contents of cell wall pectin, hemicellulose, Al, and Al-induced massive reactive oxygen species accumulation in the roots of hickory. Transcriptomic analysis revealed that MT may alleviate root tip Al stress by regulating Al-responsive and nonresponsive pathways. Co-expression regulatory network and dual-luciferase receptor assays revealed that transcription factors, CcC3H12 and CcAZF2, responded to MT and significantly activated the expression of two cell wall pectin-related genes, CcPME61 and CcGAE6, respectively. Further, yeast one-hybrid and electrophoretic mobility shift assay (EMSA) assays verified that CcC3H12 and CcAZF2 regulated CcPME61 and CcGAE6, respectively, by directly binding to their promoters. Overexpression of CcPME61 enhanced the Al sensitivity of Arabidopsis thaliana. Our results indicate that MT can improve Al tolerance of hickory via multiple pathways, which provides a new perspective for the study of the mechanism of MT in alleviating abiotic stress.

Alcaligenes faecalis Juj3 alleviates Plasmodiophora brassicae stress to cabbage via promoting growth and inducing resistance

Clubroot is a devastating disease threatening global cruciferous vegetable production caused by Plasmodiophora brassicae (Pb). We have evaluated the positive effects of the Alcaligenes faecalis Juj3 on cabbage growth promotion and Pb stress alleviation through pot and field experiments. The Juj3 strain was isolated from a healthy cabbage rhizosphere with growth-promoting characteristics and was identified as A. faecalis based on morphological traits and phylogeny. Seed germination assays revealed that Juj3 inoculation enhances cabbage bud shoot and root growth. In pot experiments, inoculation with Juj3 fermentation powder at cabbage sowing dates significantly improved the seedling biomass. Combining seed treatments with root irrigation after transplanting considerably reduced the clubroot disease index and resulted in appreciable biocontrol efficacy (83.7%). Gene expression analyses of cabbage after Juj3 inoculation showed that PR2 and EIN3 expression were significantly up-regulated. Physiologically, Juj3 inoculation enhanced cabbage chlorophyll content and root activity in a normal environment. Irrespective of whether plants were under normal environment or Pb stresses, Juj3 improved photosynthesis. Field trial analyses revealed that Juj3 exhibits satisfactory biocontrol efficacy in cabbage (51.4%) and Chinese cabbage (37.7%). Moreover, Juj3 could also enhance cabbage and Chinese cabbage biomass to improve the yield quality. These findings pave the way for future use of A. faecalis as biocontrol agents for clubroot and reveal the great potential of the rhizobacterium for plant growth-promoting applications in agriculture and horticulture.